Egyptian protesters have reacted with a mixture of alarm and defiance to a warning from the vice-president, Omar Suleiman, that there could be a coup if they do not accept the regime's timetable for a transition to democratic rule.

Abdul-Rahman Samir, a spokesman for a coalition of the five main youth groups behind the protests in Tahrir Square, said Suleiman was creating "a disastrous scenario" as demonstrations entered their 16th day, spreading from the square to the parliament building and other government offices, including the department of civil aviation.

"He is threatening to impose martial law, which means everybody in the square will be smashed," Samir said. "But what would he do with the rest of the 70 million Egyptians who will follow us afterwards?"

Khaled Abdel-Hamid, another youth organiser dismissed Suleiman's warnings. "We are striking and we will protest and we will not negotiate until Mubarak steps down. Whoever wants to threaten us, then let them do so," he said.

Protesters said the organisers were working on plans to move on to the state radio and television building on Friday, the day of the next big scheduled demonstration, and trying to draw powerful labour unions into support for their cause.

The protests are aready spreading. Teachers are going on strike and there have been walkouts in one factory in the textile town of Mahalla. About 3,000 workers in companies owned by the Suez Canal authorities and based in Ismailia and Suez went on strike on Tuesday over pay and conditions, while workers in canal-owned companies in Port Said took industrial action on Wednesday, although the crucial shipping route was operating with little disruption.

Should shipping companies, however, decide to avoid the canal and sail round the Cape of Good Hope, Egypt would lose a major source of revenue. Tolls collected reached $4.3bn (£2.7bn) from January to the end of November 2010.

Analysts from the French bank Credit Agricole estimate the crisis is costing Egypt $310m a day. Egypt's biggest tourist attraction, the Pyramids of Giza, reopened to tourists on Wednesday although tens of thousands of foreigners have fled Egypt amid the chaos.

In his comments on Tuesday night, Suleiman rejected any immediate departure for President Hosni Mubarak or any "end to the regime".

"We can't bear this for a long time," he said of the Tahrir protests. "There must be an end to this crisis as soon as possible." Speaking to editors of state and independent newspapers, he said the regime wanted to resolve the crisis through dialogue, adding: "We don't want to deal with Egyptian society with police tools."

If dialogue is not successful, he said, the alternative is "that a coup happens, which would mean uncalculated and hasty steps, including lots of irrationalities".

Osama Saraya, editor-in-chief of the pro-government newspaper Al-Ahram, who attended the meeting, said Suleiman did not only mean a military coup but a takeover by another powerful state apparatus or Islamist groups.

Mubarak has said he will step down at the end of his term in September, but the US is raising the pressure for speedy reform. The US vice-president, Joe Biden, spoke by telephone to Suleiman on Tuesday, saying the US wanted Egypt immediately to rescind emergency laws that gave broad powers to security forces, a key demand of the protesters.

While media attention has focused on developments in Cairo, protests have also occurred throughout the country. Cities across the Nile delta north of Cairo, those far to the south and others to the east have also had streets filled with demonstrators demanding Mubarak go.

"I want Mubarak to leave, I want all this system to leave, this system has all kinds of corruption," Mohamed Sabaie, a jobless 25-year-old in the Nile delta city of Tanta told Reuters.

Farmers have also voiced support for the demonstrators. "The revolution is good … It will give us stability but the protest should stop and the president should be allowed to stay until the end of his term," said Fawzi Abdel Wahab, a farmer working a field near Tanta. "If the president doesn't do as he promised, Tahrir Square is still there and the youth will not die, they can go back."

About 300 demonstrators are estimated to have died in the unrest, but a comprehensive count is a long way off as some bereaved families hesitate to come forward. Human Rights Watch continues to warn that hospitals have been ordered to play down the numbers of casualties. It has condemned the arrest of an estimated 119 people in the crackdown on the protest and says it has evidence that five of those people were tortured.

An al-Qaida in Iraq front group, meanwhile, has urged Egyptians to join holy war and establish an Islamic state – the latest in a series of statements by Islamic militants supporting the protesters. The Islamic State of Iraq warned Egyptians against being deceived by "the malicious secularism, the infidel democracy and the rotten pagan nationalism," according to a statement posted on two militant websites.